and Eskimos, killed as many as 16,000 animals per year in the 1930s. By the mid-1950s, a great depletion 0 f the walrus popula­tion had become apparent.

Recognition of the plight of the Pacific walrus sparked the beginning of research and management efforts. Independent and cooperative programs were developed by the governments of the United States and Soviet Union. In 1960, the newly created Alaska Department of Fish and Game (ADF&G) recognized the importance of walruses to coastal residents and selected that species for particular attention.

Restrictions imposed by the Soviet Union and the State of Alaska greatly reduced harvests. The estimated total kill dropped from over 9,000 in 1958 to between 3,000 and 4,000 annually during 1967 through 1974. In addition, Alaska's regulations restricted the killing of adult females so that hunt­ing pressure shifted to males. The ratio of bulls to cows in the Alaskan harvest from 1964 to 1972 was three to one.

Steps were also taken to protect walruses on coastal hauling grounds. The Walrus Islands State Game Sanctuary was created in 1960 to maintain the quality of a particularly important haul­ing area.

In 1960, researchers began counting walruses from airplanes. The techniques used in these surveys and the population estimates derived from them varied considerably for the first few years. Since 1975 a standard survey procedure, developed as part of the marine mammals project of the US-USSR En­vironmental Protection Agreement. has been used. Surveys are conducted every five years in September, with Soviet research­ers counting walruses on coastal haulouts and sea ice in the western Chukchi Sea and along the Chukchi Peninsula, while scientists from the U.S. Fish and Wildlife Service and ADF&G count animals on the pack ice of the eastern Chukchi Sea. Population estimates from these surveys were about 220,000 in 1975 and 250,000 in 1980. Although some have questioned the absolute accuracy of the numbers, all agree that walruses are now much more abundant than they were in 1960.

Harvests by Eskimos and Soviet commercial hunters are now at about 7,500 annually. Although walruses are easy to locate and identify, it is difficult to determine the status of the entire population. Since the mid-1950s, researchers have collected samples from the Eskimo harvest and anaJyzed them to deter­mine food habits, birth rates, and the condition of the animals. After passage of the Marine Mammals Protection Act in 1972, which took management of walruses (and other marine mam­mal species) away from the State of Alaska, collection of data and specimens became more irregular.

That was unfortunate because it happened when considerable changes were occurring in the walrus population. Various in­dicators of population status suggested that the population was healthy and growing during the 1960s and well into the 1970s. In about 1978, however, Eskimo walrus hunters began to report that walruses were thin, had eaten unusual foods, and that there were fewer calves in the herds. Researchers later confirmed these observations. The average thickness of blubber had decreased from 5 or 6 cm in the years 1958 through 1978 to only 3 or 4 cm in 1980 through 1983. Stomachs of walruses were examined and

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~------------------------------------------~~ sometimes found to contain fish, seals, anemones, and jellyfish, items that had rarely, if ever, been recorded in their diet previous­ly. Composition counts of nursery herds in the Chukchi Sea revealed only five to ten calves per 100 adult females, a ratio far below the 30 to 35 that would be expected in a healthy, grow­ing population. In addition, the average age of animals in the harvest had increased at all major hunting villages. Although all the details are not clear, we can be certain that major changes have occurred in the walrus population in the past few years. The population is no longer made up of fat, young adults, but consists mostly of lean, old animals, and old walruses produce fewer calves than do young adults. MortaJity among newborns and miscarriages have increased. These changes, if they con­tinue, will cause the population to decline. Whether the number of walruses has declined already will not be known until after the next joint aerial survey in September, 1985.

What caused these alarming changes? Some biologists believe that before intensive harvests by man, the walrus popula­tion in the north Pacific was between 200,000 and 250,000, and

Alaska Fish & Game 4

that the clam beds upon which walruses feed can support only 185,000 to 200,000 walruses over the long term. Probably, walruses have become more numerous than their food supply can support. In technical terms, they may have exceeded the carrying capacity of their habitat. Although this is a well-known occurrence for terrestrial mammals such as deer, the phenomenon has not been documented in marine mammals.

Since it is much more difficult to see and study the clam beds where walruses feed than the forests that support deer, we do not really know the effect walruses have had on their food sup­ply or the present condition of the clam population. However, we do know that the clams walruses eat are slow-growing, and we can assume that their recovery will be slow, even after the predation pressure by walruses has lessened. The result may well be long-term cycles in the abundance of walruses and their prey.

History has shown us that harvesting by humans can great­ly affect walrus abundance. We note with particular interest that Yankee whalers and Russian commercial hunters were able to deplete the population, while more recently, the herds grew rapidly in spite of a continued harvest by Eskimos and the Soviet Union. The scarcity of walruses during the early part of this century probably allowed the clam populations to grow.

July-August 1985

(!) 01:1 U. o c(

When hunting pressures were reduced, conditions were set for explosive growth of walrus herds. Not only was food abundantly available, but the surviving population contained a large pro­portion of young, adult females, the part of the population that inhabited the most inaccessible areas of the walrus's range. The walrus population, then, was unusually productive, and grew to the point of overgrazing the clam population upon which they depend. This is a likely scenario, but biologists are by no means certain that it is accurate. It is a theory that mayor may not be supported by the findings of the 1985 joint aerial survey by the U.S. and the Soviet Union.

Harvests in the 1980s have been the highest since the 1930s and are being taken from a less healthy and less productive population. The size and characteristics of current and future harvests will undoubtedly affect the future abundance of walruses. U.S. agencies with management responsibility or in­terests are currently the U.S. Fish and Wildlife Service, the Eskimo Walrus Commission, and the State of Alaska. These groups will need to develop management plans to ensure that the walrus population rebounds quickly following the decline phase that is apparently beginning .•

Lloyd Lowry is a game biologist with ADF&G in Fairbanks.

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